1. Field of the Invention
The present invention is a vehicle for traversing a surface such as for carrying out an inspection, survey or maintenance operation upon that surface.
2. Description of Related Art
In Patent Specification No. GB2305407A we have described a vehicle for this purpose which comprises two bodies interconnected by means to move the bodies towards and away from each other, each said body being supported upon a multiplicity of resilient bristles extending from it. Operation of that vehicle by alternate moving of the bodies towards and away from each other causes it to move in successive steps along a generally linear path over the surface upon which it is supported. The bristles are inclined by a small amount away from being perpendicular to the surface and thereby provide a grip upon that surface which is greater in one direction than in the opposite direction, as determined by the direction of inclination of the bristles.
This foregoing surface-traversing vehicle has proved to be able to move progressively and effectively over a range of different surfaces. When it is required to move in the opposite direction, for example to withdraw from a tubular conduit in which it has been operating, it is necessary for the surface-gripping effect of the bristles to be reversed by reversing the direction of inclination of the bristles. One possible way of achieving that reversal is to rely wholly upon the resiliency of the bristles and to reverse their direction of inclination simply by pulling axially upon the relevant bristle-supporting body. The reorientation of the bristles may be assisted by rotating the relevant body about its axis.
As indicated in the above patent specification, it could be advantageous if at least one of the bristle-supported bodies were constructed with retractable bristles. However the provision of a mechanically-operated system for retracting such bristles is particularly difficult in the case of surface-traversing vehicles of the present general type in that one important use of such vehicles is in the harsh environments of sewers, oil pipelines and the like, wherein deposited dirt and other sediments can readily impede continued satisfactory mechanical operations. It is perhaps not surprising that no satisfactory provision of such retractable bristles has hitherto been available.
It is therefore an object of the present invention to provide a surface-traversing vehicle of this general type in which a practical and advantageous retraction of the bristles is made possible.
According to the present invention, there is provided a surface-traversing vehicle comprising a plurality of bodies at least one moving device for moving at least one pair of adjacent said bodies towards and away from each other, a plurality of bristle-carrying members mounted to a plurality of said bodies, a plurality of resilient bristles mounted to each said bristle-carrying member, wherein each said bristle-carrying member is adapted to be moved in a respective first direction away from the corresponding said body and a respective second direction towards the corresponding said body, and at least one fluid pressure device for moving said bristle carrying members in the respective first and/or second direction thereof relative to the corresponding said body, wherein said moving device is adapted to cause said vehicle to traverse a surface by moving at least one pair of adjacent said bodies towards and away from each other when a plurality of said bristles of said body are in engagement with said surface to support the vehicle.
Thus, by operation of the fluid pressure means associated with one of the bodies, the bristles of that body may be retracted and/or extended as required, to enable their orientation to be reversed and the body to be moved more readily in its reverse direction, thereby permitting reversal of the direction of movement of the surface-traversing vehicle.
As described in Specification No. GB2305407A, the interconnected bodies which are a feature of the surface-traversing vehicles of the type to which the present invention is applied may be of various shapes depending upon the general nature of the surface to be traversed. Thus they may be generally flat or, for example, rotationally symmetrical, for example generally cylindrical. The bristles may extend generally perpendicularly from the bodies if the bodies are flat. Most usually, the bodies will be generally cylindrical and the bristles will extend generally radially outwardly or inwardly of the body. While the surface-traversing vehicle may comprise generally hollow bodies with inwardly-directed bristles, designed to enable it to progress over the outer surface of a chimney, cable or like conduit, the vehicle is particularly well adapted to use within a tubular pipe, sewer or similar conduit and for that purpose will have outwardly-directed bristles, in particular bristles directed radially outwardly.
Although in most cases the bristles are preferably directed generally perpendicularly, including radially, from the bodies upon which they are mounted, in particular when the bodies are viewed from the side relative to their direction of relative movement, when those bodies are rotationally symmetrical, the bristles may be inclined to a small extent in the rotational direction in order to discourage undesired rotation of the bodies. For example, alternate bristles or groups of bristles around the bodies may be inclined in alternate directions in a cross-ply structure to stabilize the bodies against such rotation.
The bristles of each of the bodies are mounted in groups upon a plurality of bristle-carrying members each guided for movement towards and away from the said body. These bristle-carrying members may be spaced apart at intervals over the surface of the body but preferably they combine to cover the whole of the relevant surface of the body and therefore lie closely together at one limit of their guided movement. By way of example, in the case of generally cylindrical bodies having outwardly-directed bristles, the bristle-carrying members may each form one angular segment of the cylindrical surface of the body. Preferably such segments are all of equal angular size, for example 4, 6 or 8 segments each covering, respectively, 90 degrees, 60 degrees or 45 degrees of the cylindrical surface of the body.
The bristle-carrying members are guided so that they may move towards and away from the body upon which they are mounted. Preferably that movement is generally radial with respect to the axis of a generally cylindrical body. To that general end, the axially opposite ends of each bristle-carrying member may be designed to engage generally radial slots or guide channels in the ends of the body. As an alternative, the bristle-carrying members may be mounted upon pins extending through radial apertures or bores in the body, or may themselves slide upon radial pins upon the body.
The movement of the bristle-carrying members towards and/or away from the associated bodies is effected by a fluid pressure means. It is preferred that the latter means be hydraulically, or more preferably pneumatically, operated. By way of example, when the bristle-carrying members each form an angular segment of the body, a membrane, for example a generally cylindrical tubular bag-shaped membrane, may be located along the axis of the body in contact with the radially inner faces of the members. When the membrane is caused to expand outwardly, either by stretching or by unfolding, upon the introduction of, say, compressed air into its interior, the bristle-carrying members are thereby urged outwardly. The latter members may subsequently disengage from the surface being traversed either simply in response to the absence of radially outward pressure or, more positively, under the action of one or more return springs when the fluid pressure is removed.
In one alternative form of the surface-traversing vehicle according to the present invention, the bristle-carrying members are each supported upon a plurality of inwardly-directed pistons, each arranged to slide, in response to fluid pressure on their inner ends, outwardly within radial, fluid-tight bores within the associated body. The return movement of the bristle-carrying members may, for example, be in response to evacuation of the bores and/or by the action of one or more springs and/or by the resilient action of the bristles themselves.
In yet another form of the vehicle of the present invention, in particular for use in restricted spaces such as within narrow-bore pipes, the bristles may be mounted directly upon pistons, that is, the bristle-carrying members are then themselves in the form of pistons. Typically, such bristle-carrying pistons are moved by means of a membrane, preferably a generally tubular membrane such as in the form of a thin-walled bag.
Whatever the form of the fluid pressure means by which the movement of the bristle-carrying members is effected, it is advantageous to provide also a resilient means tending to resist that movement of the bristle-carrying members. In this way, by varying the pressure of the fluid pressure means, the bristle-carrying members may be set in a selected position intermediate to their fully-retracted and their fully-extended positions. This enables the bristles to be inclined to a greater or lesser extent to take account of variations in the surface being traversed by the vehicle. By way of example, if the frictional value of the surface changes in response to variations in the surface roughness or as a result of the presence of a lubricant on the surface, the inclination of the bristles may be modified to maintain the desired level of grip of the body upon the surface. Similarly, when the vehicle is being used to traverse the interior surface of a hollow conduit, for example of a pipe, the amount by which the bristle-carrying bodies are extended may be modified in this way to compensate for variations in the internal cross-sectional dimensions of the conduit.
Such a resilient means to resist the movement of the bristle-carrying members may take various forms, including for example that of one or more springs, e.g. coil springs. In one form, the resilient means comprises one or more pieces of a resilient polymeric material, for example an annular piece surrounding an end of the bristle-carrying bodies or one such piece at each end thereof. The polymeric material may for example be of a resilient polyurethane or a natural or synthetic rubber.
When the surface-traversing vehicle according to the present invention includes bristle-carrying members whose degree of extension can be varied as described above, it is advantageous and preferred to provide one or more sensors to monitor the characteristics of the surface, for example pipe diameter and/or surface roughness, ahead of the vehicle, so that the fluid pressure within each body, and thereby the degree of extension of the bristles, may be modified to take account of any variations in the surface characteristics as the vehicle encounters such variations. The fluid pressure may be modified by the person operating the vehicle or, advantageously, using some form of automatic xe2x80x9cintelligentxe2x80x9d controller.
The resilient bristles may be of any material having the selected resiliency and may be chosen to reflect the circumstances in which the vehicle is to operate including, among other factors, the load to be supported and/or towed by the vehicle. Thus they may be natural bristles or they may be of a synthetic polymeric material, for example, or of a metal. The selected material preferably has a relatively high stiffness and a good elasticity. It is particularly preferred to use metal bristles, for example of steel, in view of the quick elastic response, and the usually better surface grip, of such metal bristles. Because, by virtue of the present invention, any required reversal of the direction of inclination of the bristles is greatly aided by the retraction of the bristles, bristles of higher stiffness may be used than would be possible if they had to be re-directed without retraction.
The vehicle moves over the surface in response to the movement of the bodies towards and away from each other. This relative movement of the bodies may be achieved by any desired means, for example by electrical power provided by an on-board source such as a rechargeable battery or by a remote source via an electrical line. However it is particularly preferred to effect relative movement of the bodies by fluid pressure, in particular by linking the bodies by a hydraulic or more preferably pneumatic cylinder.
Additional support for the bodies may be provided in the form of one or more wheels, whereby the load borne by the bristles is reduced. Such wheels may be located upon the bodies themselves or upon the links between them, for example.
In one advantageous form of the invention, wheels may be mounted directly upon one or more of the bristle-carrying members. In this way, the distance, or the minimum distance, of the bristle-carrying members from the surface under treatment may be set at an advantageous predetermined value, for example a value at which the inclination of the bristles relative to the surface is optimized.
While the surface-traversing vehicle according to the invention may comprise just two of the bristle-supported bodies, it may prove advantageous to provide three or more such bodies. For example, reversal of the direction of operation of the vehicle may be assisted by the provision of a third body and/or the movement of the vehicle overall may be rendered more smooth in this way. In one arrangement, the bodies may be coupled together in pairs, with the two bodies in each pair being coupled at a fixed distance apart, thereby increasing the effective length of each body.
Particularly when the vehicle comprises at least three of the bristle-supported bodies, it is desirable that the required relative movement of the bodies be effected automatically, for example by means of a suitable controller, which may be located either upon the vehicle or at a remote location, to which latter the vehicle may be linked by a direct line or by radio.
When the vehicle is designed to be operated pneumatically, an air line may be provided from a remote source of compressed air to the pneumatic cylinders. That line may be combined with an electrical line, in the form of an umbilical linking a remote control position to the vehicle. The umbilical may in turn be dragged behind the vehicle by means of a similar towing vehicle specifically provided for that purpose. As the vehicle proper moves further from the control position, supplementary such umbilical tugs may be added. Sensors in the line may monitor tension in the umbilical and in turn prompt an umbilical tug to respond by accelerating or decelerating briefly.